The present invention relates to an image expansion and display technique for expanding a JGEG compressed digital image data and outputting the data to a monitor built in a system or an external display device.
In recent years, a wide range of image sizes for a small size image having a small capacity and a small angle of view, represented by a VGA size image, and a large size image having a large capacity and a large angle of view, reputed to have an increased number of pixels and high image quality accompanied with increase in the number of pixels of imaging devices, have been dealt with in the digital still camera industry, the camera-equipped cellular phone industry and like industry. That is, the range of a data amount to be dealt with in such industries keeps on expanding. When a large size image having a large capacity and a large angle of view is to be processed in an apparatus which is optimized for a small size image having a small capacity and a small angle of view, a large-capacity image frame memory region which is proportional to an image size is necessary.
FIG. 4 is a block diagram illustrating the configuration of a known image expansion and display device. In FIG. 4, a header information analysis section 51 analyzes header information of a compressed image file FL which is JPEG compressed and recorded on a recording medium or the like and reads an image size after expansion. Then, a frame memory region required for expanding image data having the image size is ensured. A JPEG expansion section 52 JPEG-expands compressed image files FL successively transferred from the header information analysis section 51 and data after the expansion is successively recorded in the frame memory region 53 ensured by the header information analysis section 51. In this case, expansion is performed by MCU (8×8 pixels), as shown in FIG. 4. Respective blocks of MCUs are successively jointed to one another, thereby expanding the whole image.
Next, a resizing section 54 magnifies/reduces the image data expanded to the frame memory region 53 to an image size required for displaying an image and performs mapping of the image data to a display frame memory 55. For example, when an image is displayed on a liquid crystal monitor built in the body of a digital still camera, the image size required for display is determined from properties of the liquid crystal monitor. When a video signal is output through an external terminal such as an AV terminal, the required image size is determined from properties of an external display device to which the signal is output. As such a known technique, a technique for having an image displayed with the size of the displayed image changed so that a frame rate of a moving picture is not reduced has been disclosed (e.g., see Japanese Laid-Open Publication No. 7-23378).